This invention relates to dynamoelectric machines and, in particular, to direct cooled dynamoelectric machines of the type including a rotating field comprising electrically conductive windings disposed in a plurality of axially extending slots.
The rotating field of a dynamoelectric machine includes a rotor body having a plurality of axially extending slots into which the electrical windings are inserted. The rotor body is generally a steel material whereas the rotor windings comprise a plurality of copper wires. In a direct cooled dynamoelectric machine each slot may further include an axially extending sub-slot for ventilation and cooling. The direct cooled machine is one which is cooled directly by the atmosphere in which it is disposed; e.g., air or hydrogen. The sub-slots are part of a ventilation scheme, known in the art, for transferring gas coolant axially along the rotor. Each slot also includes provision for the radial flow of gas coolant primarily through ventilation slots in the windings.
In the afore-described machine it is necessary to electrically insulate the rotor windings from the rotor body such insulation taking the form of non-conductive "slot armor." Moreover, it has been the practice of some manufacturers to provide sub-slot covers which increase the insulation of the bottom of the slot. In a direct cooled dynamoelectric machine wherein the machine coolant is air it is possible that foreign material may accumulate on sub-slot surfaces in such a way as to reduce electrical creepage distances and lead to low insulation resistance or a grounded field.
It is one object of the present invention to provide an improved sub-slot cover for a dynamoelectric machine rotating field.
It is another object of the present invention to provide an improved sub-slot cover for a dynamoelectric machine field which increases the electrical creepage distances between the field windings and the rotor.
It is still another object of the present invention to provide an improved sub-slot cover for a direct cooled dynamoelectric machine field which reduces the possibility of inadvertent grounding of the field windings which may be caused by the accumulation of foreign deposits.
The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood with reference to the following description taken in connection with the appended drawings.